Alpha-olefin polymers stabilized with phenyl phosphine derivatives



ALPHA-OLEFIN POLYMERS STABILIZED WITH PHENYL PHOSPHINE DERIVATIVES BrianF. Street, Upton-by-Chester, and Wladyslaw. H. Skoroszewski, Davyhulme,near Manchester, England, assignors to Shell Oil Company, a corporationof Delaware No Drawing. Filed June 18, 1959, Ser. No. 821,081 Claimspriority, application Great Britain July 1, 1958 6 Claims. (Cl. 260-453)sures in the presence of certain catalyst compositions which arecommonly referred to as Ziegler catalysts or low-pressure catalyst.These catalysts may be briefly described as comprising the reactionproduct of at least one compound of a metal of group lV-VI of theperiodic table with atleast one of the following: (A). aluminumtrialkyl, (B) a compound of the formula R R AlX wherein R and R areselected from the group consisting of hydrogen and hydrocarbons and X isselected from the group consisting of hydrogen, halogen .alkoxy,aryloxy,

the. residue of a secondary amineysecondary acid amine, mercaptan,diphenol, carboxylic acid and sulfonic acid, (C) an organo zinccompound, and (D). an organoa magnesium compound. The compositionprepared from a'compound of the formula R R AlX inwhich R1 and R areselected from the group consisting of hydrogen and hydrocarbon and .X isa halogen with a metal. selected a from the group consisting of metalfrom the group VIII of the periodic table or'manganese may also be used.

Low pressure polymers of alpha-olefins may also be obtained with acatalystcomposition comprising the reaction product aluminumtrichloride, titanium tetrachloride and aluminum powder. Still othercatalysticompositions: are known for the production of polymers of alphaolefins at low temperatures and pressures but the nature of the catalystcomposition is not the important;

feature of the stabilized compositions ofthis invention,

as long as thepolymers are linear or crystalline.

Itis an'object of this invention to provideiiovel compositionsof'polymers of mono-alpha-olefins. It is an-' other object of thisinvention to providestabilized compositions of polymer of,alpha'-olefins.' "ltfis a further object of this invention to providepolymers of alphaolefins which have color stability and whichhaVeimproved resistance to oxidation. It is yet another object of thisinvention to providemethods for stabilizing linear or crystallinepolyethylene and polypropylene. It is still.

anotherobject of the present invention to prevent, or at leastappreciably reduce, tendency of the polyolefins to degrade duringprocessing (egimilling' or molding) operation which as are carried outduring the manufacture of articles therefrom and also during thesubsequent lifetime of sucharticles.

While this. invention applies equally topolymers of mono-alpha-olefinsfor the sake of convenience, the description 1 of the inventionisdirected. mainlyto poly- The linear'polyeth'ylene, prepared by thelow-pressure V processes tend to degrade and discolor "on exposure tolight and on b ein'g subjected to elevated temperatures, i.e.

temperatures above 100T. C. A number. of coinpounds ice degradationunderthe conditions indicated. In the case p of polyethylene, polypropyleneand other low-pressure polymers of monoralpha-olefins, an appreciablenumber of these known additives have. been found to be useful to reducedegradation but many of them have a concomitant adverse affect, that isof causing a marked color formaton or staining. Thus when such additivesare added to the linear. polyethylene, there is often produceddiscolor-' tional antioxidants to an objectionable extent.

Thus it has been. found that most of the antioxidants which are quitesatisfactory for use with polyethylene produced by thehigh'pressureprocesses produce this pro nounced discoloration when used inpolymeric materials based on the low-pressure polyethylene, and are thusof nocommercial usability as antioxidants. for low-pressure polyolefins.

According to the present invention, a normally solid polymer of amono-alpha olefin is stabilized by the addition of from about 0.01 toabout 5% by weight of the polymer, of an organic phosphine having theformula P(-R) (R')'(R'.') wherein R is a hydrocarbon radical. containingan aromatic nucleus and R and R are the same or different hydrocarbonradicals. In the most preferred embodiment the Rs are aromatic andmorepreferably they r are the same aromatic radicals such as phenyl,naphthyl,

anthracyl, the corresponding alkyl substituted radicals, and the like.The more preferred phosphinesare represented bytriphenyl phosphine,diphenyl decyl phosphine, diphenyl tolyl phosphine, tritolyl phosphine,diphenyl benzyl. phosphine and naphthyl .diphenyl phosphine. Althoughthe phosphine that is employed in the present invention. ranges from aslittle as 0.61 to about 5% by weight of the polymer, amounts in theorder of 0.05m to about 0.5% by weight is usually adequate.

h The organic phosphines may be incorporated into the polymer of theolefin byany suitable means such as by milling on heated rolls,extruding, Banburying, and the like. In some cases it may beadvantageous to add a small amount of base, such as an alkali metalcarbonate ing, extruding, etc. and may alsofinclude various otherjhave'beenproposed as additives to impart resistance to L s or analkaline earth metal oxide, so as to provide some residual alkalinityinthejpolymeric material. 'Ihusit has been foundthat in the presence of upto about 0.75% by weight, of polyethylene-ofarr-alkali metal hydroxideor carbonateoran alkaline. earthmetal oxide, hydroxide or carbonate. is.particularly useful for. molding materials prepared from polyethylene orpolypropylene which, acicordingtothisinvention contain residues of thelow pressurelcatalyst. It will be readily appreciated that a plural.-ity of 'phosphines of the type described above may be 7 present in thecomposition which is subjected .to the millmodifiers, as. rubber,pigments, fillers, lubricants, anti static agents, and the like.

The invention will be described in greater detail in the examples whichfollow.

. s EXAMPLEI Polyethyleneavas formed into sheets by milling thepolyethylene for 1 hour on a 2-rol1 mill with a mill surface temperatureof "approximately. C. Table I gives summaries of some comparativeresults obtained by incorporating various amounts .oftriphenylphosphiue= and a more conventional antioxidant in the polyethylene. Thefigures for color rating are obtained in a standard reflectivity testand are based on a rating of 100 for a standard white disc. Thepolyethylene used as the base Table III material had a color rating of85 on this scale. The intrinsic viscosity (I.V.) (determined as 0.1%solution Luectlontem mum in decalin at 120 c.) and the melt index (M.I.)of the 5 1 P polyethylene prior to processing was 2.25: the LV. and 2000 240 C 27000 M.I. of'the material after hot rolling provides anindication of the degree of degradation (if any) which has 84 78 takenplace. The polyethylene was prepared as indicated 237 246 262 in BelgianPatent 533,362 using aluminum triethyl-titani- 52 um tetrachloridereaction product as the catalyst.

Table I Percent, Before milling After milling Antioxidant by weight,

oi antioxidant LV. Color M.I. LV. Color M.I.

None 2. 85 0. 34 1. s3 77 0. 14 Trlphenyl phosphine 0.1 2.35 80 0.37 2.35 75 0.39

o 0. 3 2. 02 79 0. 42 2. 07 e1 0. 41 4,4 butylidene bis(3-methyl-6-tertbutyl phenol) 0. 1 2. l8 1 46 0. 4 2.13 49 0.47

1 Discoloration occurred on mixing in the conventional antioxidantbefore hot milling.

EXAMPLE II 25 EXAMPLE IV Table II Using the same fomulation as inExample III, except that the triphenyl phosphine is replaced with thesame amount, by weight, of tri-p-tolylphosphine, the resulting polymerhas substantially the same color, IN. and M1.

' EXAMPLE v Polypropylene is prepared by known polymerization processesusing titanium trichloride-aluminum diethylchloride reaction product asthe catalyst. The solid polycompression molded.

Percent change Power iactorXlO in weight Additive V 40 7 After 24 After48 At the After 24 After 48 hrs. hrs. start hours hours None +6. 07 +0.423 7 40 145 0.1% triphenyl phosphlne +0. 011 0. 001 11 13 12 0.1%Non0X',CI 0. 138 0. 184 10 7 9 1 Sym-dl-beta-naphthyl-p-phenylenediamine.

' EXAMPLE I11 Molding trials were carried out using polyethylenecontaining triphenyl phosphine. "The triphenyl phosphine was added tothe polyethylene in an amount equal to 0.2 part per hundr'ed ofpolyethylene and the resulting mixture extruded in a Buss Ko-Kneader andthe product? finally chopped in a cutter to give a molding powder: theresulting material had an I.V. of .1177, a M.I, of 2.08 and a colorrating of 86. Discs were then molded in an" injection inolder usingvarious molding (i.e. injection) temperatures. The properties of thematerial after molding were then determined and the results are given inTable III.

mer is then milled with 0.2% by'weight of diphenyl decyl phosphine. Themilled'product is then granulated and In comparison to polypropylenethat contains no phosphine, the specimen with the phosphine hassubstantially better color and flow properties. Further the LV. is notreduced severely.

We claim as our invention:

1. A composition comprising a polymer of an alpha olefin containingtitanium metallic residues and from 0.01 to about 5%; by weight, of aphosphine of the formula P(R)(R)(R") wherein R is a hydrocarbon radicalcon-y taining'an aromatic nucleus and R and R are hydrocarbon radicals.

2. The composition of claim 1 in which the polymer polyethylene. t

.3. The composition of claim 1 in which the polymer is polypropylene.

4. The composition of claim 1' in which the phosphine istriphenylphosphine. a

S. Thercomposition of claiml in which the phosphine is tritolylphosphine.

. 6. The composition of claim 1 in whichthe phosphine 2,860,115 Heckeret a1. Nov 11, l958-

1. A COMPOSITION COMPRISING A POLYMER OF AN ALPHAOLEFIN CONTAINING TITANIUM METALLIC RESIDUES AND FROM 0.01 TO ABOUT 5%, BY WEIGHT, OF A PHOSPHINE OF THE FORMULA P(R)(R'')(R") WHEREIN R IS A HYDROCARBON RADICAL CONTAINING AN AROMATIC NUCLEUS AND R'' AND R" ARE HYDROCARBON RADICALS. 